Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%

Definitions

• This invention was made in the preformance of a contract with the Department of the Air Force.
• This invention relates to the high strength nickel-base superalloy field.
• the strength and ductility of the alloy were such that it was practically undeformable and, hence, found application only in precision cast form and found utility only in those applications, such as turbine blades, where cast properties were acceptable.
• the alloy could, if desired, be readily forged, including forging to shapes such as engine discs as well as miscellaneous other forms such asshafts, rings and seals.
• the high temperature strength/low density characteristics are so favorable for aerospace applications, serious consideration was given to the expanded use of the alloy, particularly for engine discs.
• the mechanical property criteria applicable to discs differ in some respects from those required in blades and, although satisfactory performance was attained with the conventional alloy in cast form as blading, it was unsatisfactory in wrought form in engine discs.
• the blades are typically retained in fir tree notches machined in the periphery of the disc.
• the disc must, therefore, not display unacceptable notch sensitivity.
• the presence of a notch should not result in a decrease in strength at the notch, vis-a-vis the unnotched specimen of the same dimensions as the notch.
• the distribution of forces and alloy characteristics should be such that notch strengthening is exhibited.
• the notch strength of the conventional alloy was less than that of the smooth specimen, particularly in the critical 1300-1400 F. temperature range to which the periphery of the disc may become heated in operation.
• the present invention is directed to a wrought nickelbase superalloy of critical composition and wrought products produced therefrom, which, upon suitable heat treatment, produces a specific volume of the strengthening 7' phase, typically Ni (Al,Ti) together with a carbide, including the M C -type carbide, which not only maintains acceptable levels of other mechanical and physical properties but also provides notch strengthening, particularly in the 13001400 F. temperature range.
• the wrought alloy is provided at a nominal chemistry of, by weight, 12.4 percent chromium, 18.5 percent cobalt, 3.2 percent molybdenum, 4.3 percent titanium, 5.0 percent aluminum, 0.8 percent vanadium, 0.02 percent boron, 0.06 percent Zirconium, 0.07 percent carbon, balance essentially nickel. 1
• Forged products produced to the foregoing chemistry display notch strengthening in the 1300-1400 F. temperature range with oxidation resistance to at least 1600" F. when heat treated as follows:
• the fully heat treated article is characterized by a 7' volume percentage of about 50-60 percent, preferably about 56 volume percent, as compared to a more typical 70 volume percent in the usual cast alloy chemistry.
• the conventional alloy was developed for and used in the production of castings exhibiting high temperature strength and oxidation resist ance.
• the present invention contemplates wrought component applications and has been developed to produce, upo favorable heat treatment, a specific volume of intermetallic precipitates of the 'y' and M C types which provide the requisite mechanical properties, including in particular notch strengthening, in the general temperature range of 1300l400 F. This is distinct from the criteria and microstructure used for and present in the prior castings and in wrought components formulated to the same composition as such castings.
• composition which was found to be critical in several essential respects, is as follows, by weight: 11.9- 12.9 percent chromium, 18-19 percent cobalt, 2.8-3.6 percent molybdenum, 4.1-4.5 percent titanium, 4.8-5.2 percent aluminum, 0.5-1 percent vanadium, 0.016-0.024 percent boron, 0.04-0.08 percent zirconium, 0.05-0.09 percent carbon, balance essentially nickel.
• Table I provides a comparative distributional analysis of the present invention and the conventional composition in terms of their respective physical properties.
• composition This invention Conventional This Conventional This Percent Percent composition, invention, composition, invention, Hrs. el. Hrs el. hrs. hrs. hrs. hrs.
• the alloy of the present invention provides the requisite notch strengthening for sensitive forged or extruded components whereas forgings made from the conventional alloy were unacceptably deficient in this regard.
• This factor alone is determinative of the utility of the alloy in components such as turbine engine discs.
• the necessary properties have been achieved, providing an article having properties never before reproducibly attained.
• the 7' content has generally been about 70 volume percent or higher.
• the wrought alloy composition of the present invention provides a microstructure having about -60 volume percent of the strengthening '7' phase, with about 56 volume percent appearing optimum.
• the total aluminum plus titanium content of the alloy is especially critical insofar as these elements are the principal determinants of the amount of the 7 phase which is formed.
• the alloy two carbide phases appear present, including a Cr C carbide distributed along grain boundaries and a TiC carbide distributed intragranularly.
• the Cr C carbide precipitated at the grain boundaries is the phase of importance to the present invention for it produces a region of localized plasticity which can undergo microstrain and provide the necessary delay to failures attributable to grain boundary efiects.
• the carbon content is especially critical in this alloy.
• a wrought nickel-base superalloy article having a nominal chemistry which consists essentially of, about by weight, 12.4 percent chromium, 18.5 percent cobalt, 3.2 percent molybdenum, 4.3 percent titanium, 5 percent aluminum, 0.8 percent vanadium, 0.02 percent boron, 0.06 percent zirconium, 0.07 percent carbon, balance essentially nickel, and characterized by V-notch strengthening in the temperature range of 13001400 F.
• An article according to claim 1 which is also characterized by a microstructure in the fully heat treated condition exhibiting 50-60 volume percent of a 'y' intermetallic phase.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Forging (AREA)
• Heat Treatment Of Nonferrous Metals Or Alloys (AREA)

Priority Applications (10)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23148872

Family Applications (1)

Country Status (10)

Cited By (3)

• 1972
  • 1972-10-16 US US00298068A patent/US3843421A/en not_active Expired - Lifetime
• 1973
  • 1973-10-03 IL IL43363A patent/IL43363A/en unknown
  • 1973-10-04 CA CA182,691A patent/CA1000077A/en not_active Expired
  • 1973-10-10 FR FR7337982A patent/FR2202948B1/fr not_active Expired
  • 1973-10-10 AU AU61219/73A patent/AU472385B2/en not_active Expired
  • 1973-10-12 SE SE7313887A patent/SE396092B/xx unknown
  • 1973-10-12 IT IT30055/73A patent/IT998742B/it active
  • 1973-10-15 GB GB4798073A patent/GB1436449A/en not_active Expired
  • 1973-10-15 JP JP11567073A patent/JPS5632391B2/ja not_active Expired
  • 1973-10-16 DE DE2351874A patent/DE2351874C3/de not_active Expired

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